1. Field of the Invention
The present invention relates to a particle arrangement apparatus and a particle arrangement method.
2. Description of the Related Art
Recently, research and development has been carried out actively for obtaining electronic devices that use fine particles (nanocomponents) whose one side is smaller than 1 μm. A field-effect transistor (FET) using semiconductor nanowires for channels has been disclosed as an example of the electronic devices that utilize nanocomponents (D. Wang, et al., “Germanium nanowire field-effect transistors with SiO2 and high-k HfO2 gate dielectric”, Appl. Phys. Lett., Vol. 83, pp. 2432, 2003). The nanocomponents such as semiconductor nanowires can be arranged on a substrate by coating. Therefore there is a possibility that the semiconducting devices that use nanocomponents may be produced at low cost as compared to conventional semiconducting devices that are formed using a large-sized vacuum deposition apparatus.
In order to obtain a transistor that uses columnar nanocomponents, it is necessary to connect a source electrode to one end of each nanocomponent and a drain electrode to the other end. To do so, nanocomponents need to be uniaxially oriented and arranged in a channel region of the transistor. Accordingly, in order to form a field-effect transistor using nanocomponents by the coating method, it is necessary to establish a production technique for orienting and arranging nanocomponents in a specific region.
A method, in which liquid passages are formed for a liquid to flow at the substrate surface and a liquid containing nanocomponents dispersed therein is passed through the liquid passages, has been reported as a method of controlling the direction in which the nanocomponents are oriented and the position where they are arranged (Y. Huang, et al., “Directed Assembly of One-Dimensional Nanostructures into Functional Networks,”, Science, vol. 291, pp. 630, 2001, and U.S. Pat. No. 6,872,645). In this method, a liquid containing nanocomponents dispersed therein is passed and thereby columnar nanocomponents are oriented and applied onto the substrate. The liquid passages located at the substrate surface are formed with a polydimethylsiloxane mold having a large number of fine grooves formed at the surface thereof that is brought into contact with the substrate.
Another method also has been reported (U.S. Pat. No. 6,969,690). In this method, a suspension containing nanocomponents whose surfaces have been rendered hydrophilic is prepared first. Next, a substrate with a surface, a part of which has been rendered hydrophilic, is brought into contact with the suspension. Thereafter, the suspension is separated from the substrate. It has been reported that in this stage, the utilization of the interfaces of solid/liquid/gas between the substrate, suspension, and air allows the nanocomponents to be oriented to a certain degree and to be placed in the hydrophilic portion of the substrate. Furthermore, a method of dipping a part of a substrate into a suspension and gradually evaporating the solvent of the suspension has been reported as a method of separating the suspension from the substrate.
However, in the method of Y. Huang and a method described in U.S. Pat. No. 6,872,645, a mold with a microstructure is used and therefore there is a problem in that nanowires are difficult to arrange on a large area substrate.
Furthermore, in the method described in U.S. Pat. No. 6,969,690, in order to increase the density at which the nanocomponents are arranged, it is necessary to pull up the substrate very slowly. Therefore this method is not suitable for mass production, which is a problem. Moreover, in this method, the center and the end faces of a substrate tend to be different from each other in density at which the nanocomponents are arranged, and therefore it is difficult to uniformly apply the nanocomponents to the whole substrate surface, which is a problem.
Furthermore, in the conventional method described above, a large amount of dispersion is required and thereby the production cost increases, which is a problem.